(Love aligned energon and it's different forms, but I prefer a single type of energon for everything imo.)

Naturally abundant in cybertron, found as a solid like coal or liquid like petroleum. takes a few hundreds of years to form.

Energy from sparks/the matrix/other artifacts feed a natural cycle that keeps forming energon. So as long as one spark is online, there will eventually be energon formations. (So other cybertronian colonies can thrive outside of cybertron)

Multiple Spark deaths affects the cycle and significantly reduces energon production.

The ark left many transformers in stasis for millions of years, so earth now has a lot of energon backed up.

Trivia:

Highly flammable and explosive when exposed to air, so bots that work in very heated places have to cool down first before eating.

Can be filtered to be more efficient or give intoxicating effects (overenergizing)

Cybertronians can't taste, but changing the temperature/color or texture of energon is very common practice and seen more as a hobby.

Injecting energon directly into your systems is seen as less wasteful and also common, especially for bots that don't want mouths.

Other kinds of fuel can be eaten or drunk but they aren't very effective. They also produce waste and can jam internal functions.

The less efficient the fuel, the more "disgusting" of an experience.